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Tom Senior M1 Mill Arbour thread

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graham williams 111/06/2010 14:38:03
13 forum posts
All the info I can get tells me that the horizontal arbour drawbar thread is 1/2" whit........ mine isn't, it is the right drawbar.  Tried whit/bsf and even metric to no avail, think that it may be 1/2" unc, as near as I can tell it's 13TPI, which I think is strange on a British machine of the period, a thread that no one seems to carry any more, so can't try a bolt first.  Any one out there be able to tell what their M1 mill arbour is threaded?
Steve Garnett11/06/2010 22:34:22
837 forum posts
27 photos
If nobody else comes up with a definitive answer, I'll have a look at the one I have currently in storage some time over the weekend and see if I can figure it out.
Niloch12/06/2010 08:57:39
371 forum posts
Have you asked the Tom Senior Yahoo discussion group  here for an answer?
graham williams 112/06/2010 22:44:28
13 forum posts
I am unable to access the yahoo forum at work due to security protocols and do not have the internet at home - which is why i posted the question here.
 
any help     appreciated
Steve Garnett13/06/2010 01:06:49
837 forum posts
27 photos
FWIW, I looked all through the forum before posting, and there was nothing actually in it, so it would have to be a question there anyway. I'll look at the real thing first though, probably tomorrow. I know mine has a drawbar, because I remember removing it during disassembly.
Steve Garnett13/06/2010 20:56:36
837 forum posts
27 photos
Okay, it is checked - and I think I can see why you might have been having some difficulty with this, if it's anything like mine...
 
Yes, the drawbar is clearly meant to have a 1/2" Whitworth thread, and for all I know the thread cut into the M3 taper is correct, although since I can't find my 1/2" Whit tap to check this, I haven't yet. But the thread cut onto the drawbar itself isn't quite 12 tpi - it's actually about 12.2 tpi, and that's enough to bind the thread after a few turns, assuming that it's cut correctly. But there's the rub; it isn't cut correctly at all - it's a pretty loose fit, and after about an inch it's slightly malformed anyway. The thread OD measures 0.495", and whilst that's only slightly undersize, I'd say from looking at it and running a thread chaser along it that it's cut pretty deeply, and that's why it goes in sufficiently. With a bit of effort at the end, I can just get it to screw in for about an inch by hand, which is how far in it's tapped. I think that it should have gone in a lot more easily.
 
The overall dimensions of the drawbar are that the shaft is 15" long, and the last 1.5" of this are threaded. It has a 7/16" Whit head on the end, and yes I'm pretty convinced that this is original.

Edited By Steve Garnett on 13/06/2010 20:57:41

graham williams 114/06/2010 12:05:53
13 forum posts
Hi Steve,
 
Thanks for all the trouble you've gone to regarding the drawbar thread..
 
 
Managed to find a 'hole in the wall'  nuts and bolt supplier locally, been past the road lots of times and didn't even know it was there, and  he's got lots of old imperial measurement thread stock, some ex GKN and he's given me a UNC bolt to try which I've just done and it fits properly so going to go with that. Interestingly checked the main thread on the other end of the Arbour ,which is a lot easier to do, and that's measuring 1" UNF......... strange.
 
Your help greatly appreciated, many thanks.
Steve Garnett14/06/2010 14:17:23
837 forum posts
27 photos
Bit unlikely that they'd really be UNC - hardly anybody here was using UNC in the early 50's, which is when my TS was built. I still think that it's a badly fitting Whitworth, although I can see why a 1/2" UNC would sort-of fit.
 
Since mine was clearly, erm, 'mullered' somewhat, I took a careful look at it, and then ran a 1/2" UNC die over it anyway. It took off about as much metal as I would have expected to have come from converting a 55(ish) degree pitch to a 60... and it still jammed in the arbour. So I ran a tap down that, and now it's slightly on the loose side. This doesn't particularly bother me for two reasons; the drawbar doesn't exactly need to be done up ridiculously tightly, and anyway it would be very easy to make a new one with a proper 1/2" UNC thread, which will work much better - I tried an accurately cut thread in the arbour, and that's fine. I will probably make a new drawbar anyway, because the other thing I've noticed about the old one is that it's very slightly bent, and is in far worse condition than the rest of the arbour, which is in very good condition indeed.
 
But what size arbour have you got for it to have a 1" UNC at the other end? Mine's a 1" arbour, and the thread at the other end is considerably smaller than that - the thread OD is only 3/4", and it's 12 tpi, and that makes it very clearly a 3/4" BSF, because nothing else at that size uses that pitch.

Edited By Steve Garnett on 14/06/2010 14:19:00

graham williams 115/06/2010 10:55:35
13 forum posts
Hi Steve.
 
Went back to the bolt supplier to return the 1/2" UNC bolt he lent me to test the Arbour and bought a galvanised 18" bolt which when I got back didn't fit................ that's got to go back..
 
Tried 1/2" whit tap and piece of allthread again in the arbour and they both locked up within 1/2 turns, the thread in the arbour looks undamaged so didn't want to force the tap.
 
Beginning to think the Arbour wasn't one supplied by Senior, the taper and drive dogs fit and it looks the right length, i've blued them both to check but the threads are real odd unless they changed something in later machines, the serial number of mine is in the 4000's
 
The ' spacer's ' diameter seem ok and they fit the support casting/bearing at the end of the overarm, tho' it did come with another bush the correct i/d but approx 1 1/2" dia and 3 " long which I assumed was just an odd packing piece.
 
 
Ian S C15/06/2010 11:13:59
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7468 forum posts
230 photos
Remember UNC is 13TPI/Whit 12TPI. Ian S C
Boldminer15/06/2010 12:03:51
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41 forum posts
13 photos
Hi Graham, just read your post re: drawbar thread. I have a Tom Senior M1 ( No.3190) and I have just been to check it for you. My drawbar is 16.375" long, as a nominal shank dia. of .5" (.498"measured) and a thread length of 1.625". The thread measured .490"od and the 'Whit' thread gauge of 12 tpi. fit perfectly. I would therefore assume that this is just a loose fitting 1/2"Whit form.  It as always been an easy fit in the arbour, down to the last thread. Hope the info can be of use.
Steve Garnett15/06/2010 21:26:00
837 forum posts
27 photos
I'm sure that things could easily have changed over the years, and as far as I can make out the firm was rather 'pragmatic' about the way they did things anyway - Boldminer's drawbar is definitely longer than mine, although similar in other respects. My M1 is actually a pretty early one that's about the same age as me, dating from the early 50's. Believe it or not, I'm only its second owner, and yes I knew the first one quite well. Still needs a lot of work done to it though...
graham williams 116/06/2010 07:47:56
13 forum posts
Thanks Boldminer and you again Steve.
 
Have brought the Arbour with me to work this morning and going to take it to the bolt supplier to see what he has. I've noticed it's marked J/S 2000/202 on the flange above the taper which is 30int, don't know if that's significant or not. Arbour has got to be 'Aftermarket' I think but if it fits and is usable then that's it for me. Thanks for all the info.
 
 
Steve Garnett16/06/2010 09:51:14
837 forum posts
27 photos
The 30int arbours are definitely later ones, and if Boldminer's is also a 30int, that might explain the difference in overall length of the drawbar. You have to be a tad careful with this 30int thing though, because the 3MT arbour also has a locking cutout in the end of it that makes it look suspiciously similar at first glance. I don't really know why they changed this, because to all intents and purposes, a 3MT female with a locking slot cut across the end and 30int perform in pretty much the same way.
 
If I get time later, I'll post a picture of my arbour, so you can compare.

Edited By Steve Garnett on 16/06/2010 09:53:20

Ian S C16/06/2010 13:59:10
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7468 forum posts
230 photos
Arbour:bower, shady retreat with sides and roof formed mainly by trees or climbing plants. Arbor: axle or spindle on which something revolves.Ian S C
graham williams 116/06/2010 14:28:08
13 forum posts

 
Thank you for advising of my spelling mistake Ian, my English lecturer at University would have been appalled if I'd made a mistake like that. LoL.
Seriously tho' what a brilliant facility to have access to such as this, so that the like minded can attempt to get questions answered, thanks Model Engineer. GW .
Steve Garnett16/06/2010 21:26:39
837 forum posts
27 photos
Posted by graham williams 1 on 16/06/2010 14:28:08:

 
My English lecturer at University would have been appalled if I'd made a mistake like that.

My University linguistics lecturer wouldn't, though - we'd merely have had an interesting discussion about it, and somebody would have looked it up and pointed out that all we were really doing was using the American spelling of the word...
 
Well, shame on us for that, but really, what the heck?
Terryd16/06/2010 22:44:38
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1946 forum posts
179 photos
Hi Ian,
 
That's either a coincidence or plagiarism,  I've already pointed that out on another thread.
 
 
 
Hi Steve,
 
I'm not sure about your treatise on the  American spelling of arbour, according to Wikipedia a mandrel is:

"in American English also called an arbor (my emphasis),  is either an object used to shape machined work; a tool component that grips or clamps materials to be machined; or a tool component that can be used to grip other moving tool components."
 
best regards
 
Terry
 
 
 'Two nations divided by a common language'
Steve Garnett16/06/2010 23:03:18
837 forum posts
27 photos
Try Websters - at least this was written by American lexicographers, rather than just anybody...
 
It suggests that they are alternative spellings of the same word, although it has two distinct meanings, just to confuse people, and it does. If you want to find out just how much confusion there is, look at
 
http://onlinedictionary.datasegment.com/word/arbor
 
 
 

Edited By Steve Garnett on 16/06/2010 23:05:18

graham williams 117/06/2010 06:34:21
13 forum posts

 
Hi all.
 
And all I asked about was Arbo(u)r thread. LoL.
 
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